1. Field of the Invention
The present invention relates to catalysts for the polymerization of olefins. In particular, it relates to high activity catalysts for the polymerization of olefins obtained from cyclopentadienyl compounds of a transition metal, organometallic aluminum compounds and water.
The invention also relates to processes for the polymerization of olefins carried out in the presence of the catalysts of the invention.
2. Description of the Prior Art
Homogeneous catalytic systems based on metallocene compounds, aluminum alkyl compounds and water are known to be active in the polymerization of olefins.
In European Patent Application EP 384,171, catalysts for the polymerization of olefins are described which comprise the reaction product of:
(a) a metallocene compound of the formula: EQU (C.sub.5 R'.sub.n).sub.m R".sub.p (C.sub.5 R'.sub.n)MX.sub.3-m PA1 (b) an alumoxane of the formula: ##STR1## PA1 (A) a cyclopentadienyl compound of the formula: EQU (C.sub.5 R.sup.1.sub.x-m H.sub.5-x)R.sup.2.sub.m (C.sub.5 R.sup.1.sub.y-m H.sub.5-y).sub.n MQ.sub.3-n PA1 (B) an organometallic aluminum compound of the formula: EQU AlR.sup.4.sub.3-z H.sub.z PA1 (C) water. PA1 (A) a cyclopentadienyl compound of the formula (I): EQU (C.sub.5 R.sup.1.sub.x-m H.sub.5-x)R.sup.2.sub.m (C.sub.5 R.sup.1.sub.y-m H.sub.5-y).sub.n MQ.sub.3-n (I) PA1 (B) an organometallic aluminum compound of the formula (II): EQU Al(CH.sub.2 --CR.sup.4 R.sup.5 R.sup.6).sub.w R.sup.7.sub.y H.sub.z (II) PA1 (C) water; PA1 (A) a cyclopentadienyl compound of the formula (I): EQU (C.sub.5 R.sup.1.sub.x-m H.sub.5-x)R.sup.2.sub.m (C.sub.5 R.sup.1.sub.y-m H.sub.5-y).sub.n MQ.sub.3-n (I) PA1 (B') the product of the reaction between water and an organometallic aluminum compound of the formula (II): EQU Al(CH.sub.2 --CR.sup.4 R.sup.5 R.sup.6).sub.w R.sup.7.sub.y H.sub.z (II) PA1 linear, non-conjugated dienes such as 1,4-hexadiene trans, 1,4-hexadiene cis, 6-methyl-1,5-heptadiene, 3,7-dimethyl-1,6-octadiene, 11-methyl-1,10-dodecadiene; PA1 monocyclic diolefins such as, for example, cis-1,5-cyclooctadiene and 5-methyl-1,5-cyclooctadiene; PA1 bicyclic diolefins such as for example 4,5,8,9-tetrahydroindene and 6 and/or 7-methyl-4,5,8,9-tetrahydroindene; PA1 alkenyl or alkyliden norbornenes such as for example, 5-ethyliden-2-norbornene, 5-isopropyliden-2-norbornene, exo-5-isopropenyl-2-norbornene, 5-vinyl-2-norbornene; PA1 polycyclic diolefins such as, for example, dicyclopentadiene, tricyclo-[6.2.1.0.sup.2.7 ]4,9-undecadiene and the 4-methyl derivative thereof;
wherein (C.sub.5 R'.sub.n) is an optionally substituted cyclopentadienyl group and two or four R' substituents of one and the same cyclopentadienyl group can form one or two rings having 4 to 6 carbon atoms, R" is a divalent radical bridging the two cyclopentadienyl groups, X can be for instance an halogen atom, M is a transition metal selected from Ti, Zr and Hf, p is 0 or 1, m is 0, 1 or 2, when m=0 then p=0 and when p=0 at least one R' substituent is different from hydrogen, n=4 when p=1 and n=5 when p=0; and
wherein the substituents R can generically be alkyl, alkenyl or alkylaryl radicals having 2-20 carbon atoms.
The alumoxanes (b) are prepared by reacting the corresponding trialkylaluminum compounds with water in a molar ratio of 2:1. In the embodiment examples, alumoxanes are used in which the R substituents are ethyl, isobutyl or 2-methylpentyl groups.
European Patent Application EP 575,875 describes homogeneous catalytic systems for the polymerization of olefins comprising:
in which M is Ti, Zr or Hf, C.sub.5 R.sup.1.sub.x-m H.sub.5-x and C.sub.5 R.sup.1.sub.y-m H.sub.5-y are equally or differently substituted cyclopentadienyl rings and two or four substituents R.sup.1 of the same cyclopentadienyl group can form one or two rings having from 4 to 6 carbon atoms, R.sup.2 is a bridging group which links the two cyclopentadienyl rings, the substituents Q are preferably chlorine atoms, m can be 0 or 1, n can be 0 or 1, being 1 when m=1, x is an integer comprised between m+1 and 5, y is an integer comprised between m and 5;
wherein the substituents R.sup.4 are alkyl, alkenyl or alkylaryl radicals containing from 1 to 10 carbon atoms, which may also contain Si or Ge atoms, at least one of the substituents R.sup.4 being different from a straight alkyl group, z being 0 or 1; and
The molar ratio between the organometallic aluminum compound and the water is comprised between 1:1 and 100:1. In the embodiment examples, only triisobutylaluminum and triisohexylaluminum are used as the organometallic aluminum compounds.
However, the catalysts described in the above cited patent applications have activities in the polymerization of olefins which are not completely satisfactory.
Therefore, the problem which the present invention sets out to solve is to improve the activities of the above discussed known catalysts.